As an impact tool for fastening a screw, a bolt or the like, an oil pulse tool of generating a strike force by utilizing a hydraulic pressure is known. The oil pulse tool is characterized in that an operating sound thereof is low since metals are not impacted to each other. As an example of disclosing the oil pulse tool, there is, for example, PTL 1, a motor is used as a power of driving an oil pulse unit, and an output shaft of the motor is directly connected to the oil pulse unit. When a trigger switch for operating the oil pulse tool is pulled, a driving power is supplied to the motor.